Big Shoulders Stats: Finishing times

People say times don’t matter in open water – or at least that you don’t always know what they mean. And perhaps that’s part of its attraction. While in the pool “the clock never lies,” in open water it’s not much more than a ranking device.

Even so, I’ve been surprised by how closely most of my open-water pace times have approximated my pool speed at various distances – from 1:15 at 1 mile (Huntersville), to 1:17 at 1.5 miles (Livermore), to 1:19 at 2 miles (H’ville again) up to 6K (Windsor), and 1:22 at 10K (Noblesville).

When an event has been staged for many years, though – at the same location, on the same course layout – comparing times makes a little more sense. Big Shoulders is one such event.

In that spirit, here are the finish times in Big Shoulders across the 12 years of available data, starting with the 5K race:

5K times

That chart is a little busy, so let’s unpack it:

  • Each black dot represents one swim. The dots are “jiggered” slightly to the left or right of their corresponding year (so more of them are visible). If a dot is closest to the vertical line indicating 2005, that means the swim took place in 2005.
  • The blue line connects the slowest swim in each year.
  • The green line connects the fastest swim in each year.
  • The red line connects the median swim in each year.

Make sense? Now, here are the 2.5K swims over the years:

2.5K times

What does it all mean? While the slowest and fastest swims each year will depend on “who shows up,” I think we can interpret the median swim as a broad measurement of “conditions.” In Lake Michigan, that generally means water temperature and/or surface chop (but usually not current).

For a swim in the same location, with the same course layout, which draws a reasonably large sample from the same population (people who live within a few hours’ drive of Chicago), we wouldn’t expect the median finish time to vary much over time. To the extent that it does vary, we can probably attribute it to “conditions.”

One probable exception is 2003, in which both the median and fastest times were substantially faster than usual. Not surprisingly, on an anecdotal level, it was widely assumed among those who participated in 2003 that the course was shorter than 2.5K.

2 thoughts on “Big Shoulders Stats: Finishing times”

  1. I am surprised that the median times are more or less in the noise for the USMS Championship years. As shown in another stat blog participation clearly went up, but it does not appear that was more elite swimmers making the trip.

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